We studied imidazolium-based ionic liquids mixed with multiwall carbon nanotubes using impedance spectroscopy and nuclear magnetic resonance. The results show a percolation threshold below 1 wt% of carbon nanotubes, which, due to their high dispersibility in imidazolium-based ionic liquids, is 3- to 8-fold lower than the percolation threshold for carbon nanotubes in typical organic solvents. The addition of carbon nanotubes appears to polarize their interface with imidazolium-based ionic liquids and increases the diffusion coefficient of the anions up to 35%, which is likely due to weak van der Waals interactions between the carbon nanotube walls and the cations. These effects produce a 3- to 5-fold increase in electrical conductivity of the electrolyte mixture, at carbon nanotube concentrations that are under the threshold for percolation. (C) The Author(s) 2014. Published by ECS: This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: [email protected]. All rights reserved.